The present invention relates generally to saving power in portable graphics systems, and more particularly to using non-lossless compression to save power in portable graphics systems.
The number and type of portable, battery-powered electronic devices has proliferated the last few years with the increasing popularity of laptop computers, personal digital assistants, cell phones, and the like. Others, such as portable book readers (e-books), gaming, and video systems are set to become ubiquitous in the near future. These devices save time, increase efficiency, and provide entertainment.
But these devices have a dark side. Their batteries are in constant need of recharging. Accordingly, it is very desirable to reduce the power consumed by these battery-powered electronic devices, since any reduction in power lengthens the time before recharging is required.
In some devices, such as laptop, notebook, or tablet computers, much of the power dissipation occurs in the graphics system including the graphics processor, frame buffer memory, and display. Data transfers between the graphics processor and its frame buffer memory are the cause some of this power dissipation.
In some portable laptop computer architectures, data is transferred between a frame buffer memory located in a system memory and a graphics processing unit (GPU) located in an integrated graphics processor (IGP). This path includes two buses: a memory bus connecting the system memory to a central processing unit (CPU) and a host bus connecting the central processing unit to the integrated graphics processor. Output circuits that transmit data over these buses must drive integrated circuit pin capacitance, bus trace capacitance, and other stray capacitances. Driving the capacitances of these buses consumes a substantial amount of power. Also, each time data is transferred, the central processing unit, if it is not otherwise occupied, has to wake from a reduced power state to perform the data transfer.
Thus, what is needed are circuits, methods, and apparatus that reduce the number of data transfers that take place between a system memory and a graphics processor.